Automatic shaft positioning apparatus



y 29, 1952 H. M. SCHWEIGHOFER 5r A| 2,604,965

AUTOMATIC SHAFT POSITIONING APPARATUS Filed July 26, 1949 3 Sheets-Sheet 1 T fi'f w 7Z3 ATTORNEY y 29, 1952 H. M. SCHWEIGHOFER ETAL 2,60

AUTOMATIC SHAFT POSITIONING APPARATUS Filed July 26, 1949 3 Sheets-Shet 2 Aos s S. ffl

INVENTORS J y 29, 1952 H. M. SCHWEIGHOFER El'AL 2,604,965

AUTOMATIC SHAFT POSITIONING APPARATUS Filed July 26, 1949 3 Sheets-Sheet 3 0 Q I INVENTORS w: 89

Patented July 2 9, 1952 AUTGMATIC SHAFT POSITIONING APPARATUS Horst M. Schweighofer and Ross S. Pyle, Cedar Rapids, Iowa, assignors to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Application July 26, 1949, sesame. 105,945 14 Claims. (01. 162-142 p This invention relates to selective shaft 'rotation apparatus, and more particularly to arrangements for selectively controlling the angular orientation of a shaft by remote means.

The invention is in the nature of an improvement upon the'type of shaft controlling mechanism disclosed and claimed in various prior patents, of which U. S. Patent No. 2,285,414, granted June 9, 1942 to Arthur-A. Collins, is typical. i

The invention is also in the nature of an improvement upon the type of shaft controlling mechanism disclosed and claimed in application Serial No. 639,198; filed January 5," 1946, now Patent No. 2,585,955, issued February "19, 1952;

Th'e general type of control mechanism disclosed said patent requires that the shaft whichis to be selectively set, must first'rotate to a fhomeposition-or stop, and then its direction of rotation is automatically reversed until it arrives at the desired final setting. While this prior'arrangement has been'found very successful inmost fields of use, it is not entirely ole-' sirable' -wh'ere, for practical requirements, the shaft which is to be controlled cannot be first brought to a. home position in moving from a previous-selective setting to a subsequent selective setting. For example, in the'automatic control of the-flight of aircraft, guided missiles and the like Whose direction, speed, altitude, or attitude, is to be automatically controlled,-it is not ordinarily feasible torotate the-shaft which is to be controlled to a "honiefiposition or-stop for each *successivecontrol operation or cycle.

;Accordingly, one-o'f the principal objects of this invention isto provide an automatic shaft positioning "control mechanism which automatically rotates the shaft in either direction from a previous seleotive setting to a subsequent selective setting without requiring it to go to a "home position in orderto complete-the setting.

The type of device disclosed in prior application Serial No. 639,193, now Patent No. 2,585,955, issued February 19, 1952, represents a'modificatio'nof the device of the said Patent 2,285,414, in that the shaft to be controlled rotates in only one direction. f While this latter improvement represents a simplification in the control mechanism, itidoes' not permit the mechanismfto opcrate in the most expeditious manner. For example, if the shaft is designed to rotate in a clockwise direction, it may require almost an entire revolution for it to reach a-succeeding set- ;ting, when the succeeding setting is-closely ad- Jace'nt theprevious setting (when considered the shortest angularspaqing between-apr,

.ganization, arrang mentand ela ive in counter-clockwise), but is widely spaced iron; the previous setting (when considered .oloclie wise). v

Accordingly, another principal object of this in nti is to p o a m hae sm 9i tho-s e: eral type disclosed in said Patent #2285414, wherein the,stopeontrolmechanism {or the shaft iom oa lr rotates, i aoirooiion representing select ve; ettin a s b q nt i o ivl itt n I 3 I 1 Another ect 'o e v nt on "-iQzP QV iQ anautom-atic shattpositioning deviceof the type having aplurality -o f;-shi tah1e pawls, on or each-set in o "the haf -to b9 oo t i h liih pa l ar rn? cont o led-bra se ec iv y. ot m d m; and w o Qpora -.:W ii 99 o d e stop g dru t enails-Sha t mi e selective setting. The stpp ring drum andpam um a pro i e Wit a mo ora da ir io ly-s ns i mo r con rol :C I li 4 119 ie he stopri -drum; ownie-throu th she so? a ion an l o ssa y o roac hos -Sire? selective setting.- M

A fe ure of the invent o z oi ios to th so??? n tion o a o tabl ioam r-uman M is -ab e op r ng-dru whose J t sett gs det rm e the seleotiv 'se tine f any on -o a-so i leotiveshafit p nsrew s; Thodi ooti nono xte tof r tatio of the d ms s controlled by the combination o di oo iona lye o itivo switcha am tiroin witoh the al -i mail? seeking type. V I. HWY. Another feature relates to ceovola io rin drum o a m chanism o the lsi- -di 10.564111! said Pa ent '#12;28 -14, hav n nov l-in ior; but manually presettalol .sto ngs tomamio i a predetermined sequential order of selective s ping; of the rin s withrespeottto assi nedso.- lective stoppin poj o s'o tho-sheat woo controlled. I I M A still further fea ur relates-tome nerd-9.. CQH ne'c ion or pari's which coo e ate to prov; o mproved and emcient ser o m o ani m 8 111 ing cooperating & stop rings. eleoto looms, r ad 'shiftable shaft-stoopingpaw s; v ."Other featuresand advanta es not-particul 1y numerated, will be appare t a ter-a con ideration=of the followi detai edde or ptio sand the-appended claims. V In the drawin whi h re resent iby WfldkQi' an arrangementaccoi'ding toatheinvention;i..,;-,

Fig. 2 is a sectional view of Fig. 1, taken along the line 2-2 thereof, and viewed in the direction of the arrows.

Fig. 3 is a bottom view of Fig. 1.

Fig. 4 is a schematic structural and circuit diagram of the arrangement shown in Figs. 1 to 3.

Fig. 5 is a longitudinal sectional view of the stop ring drum of Figs. 1 to 4.

Fig. 6 is a left-hand face view of one of stop rings.

Fig. 7 is a sectional view of Fig. 6, taken along the line 1-1 thereof.

Fig. 8 is a right-hand face view of one of the stop rings.

Fig. 9 is an exploded view of the stop rings.

Referring more particularly to Figs. 1, 2 and 3, the device according to the invention is arranged as a self-contained unit mounted between end plates in and H, which are held in appropriatespaced relationship by tie rods l2, l3, l4. Shaft li'represents the shaft whose rotation and stopping is to be selectively controlled, and it is provided with suitable ball-bearings IE mounted on theend plates 10,- H. A stop ring drum i1 is mounted on shaft l5, and has a clamping ring H; which is capable of sliding-movement along the shaft by being slidably keyed thereto. The clamping pressure on ring I8 is controlled by a rotatable handle I-9 associated with a stud (not shown) coaxial with shaft i5, and threaded therein so as to cooperate with member It; A dial 20 is fixedly mounted on shaft 15 externally ofthe end plate ll. Drum l'i rotatably supports onits periphery the desired number of stop rings 2IA--2-l J-. These rings are adapted to be clamped together to constitute in effectaunitary assembly or barrel by' means of clockwise rotation of handle l9,fwhich causes the rim of member l8 to be displaced to the right, as viewed in Fig. l. The clamping pressure at the opposite end of the series of stop rings is against a flange (not shown) on drum 11. Thus by loosening the handle 19, the stop rings can be individually adjusted around the axis of drum i7, and when so adjusted, they can be clamped together as a unit by tightening handle l9. Each of the stop rings 2lA-2|J has a peripheral notch 23A-23J, and the peripheral orientation of each notch around shaft l5 determines a corresponding angular stopping position of that shaft when the stop ring containing that particular notch is stopped by the entry therein of the toe 3lA-'-3IJ of a corresponding shiftable stopping pawl 26A26J.

In accordance with one the feature of the invention, the stop rings are interlocked by respective pins'and grooves so that they can be independentlyand'manually pre-adjusted around the axis of shaft 15 through respective angular segments. The purpose of this interlocking is to make sure that each position of shaft I5 shall progress angularly in the same direction from the preceding position. For example, let it be assumed that the shaft 15 is to'operate the vertical elevators of an aircraft control, and that this control is designed to have ten different settings. It is necessary that these settings be in the following order, so far as angular rotation of shaft i5 from its first setting is concerned, namely, #1 #2 #3 #l0. This is necessary because the sensing control circuit of the motor that drives shaft I5 obtains its information from the respective shaft position number. If a higher numbered position of the series is to be selected for shaft [5, th motor will drive that shaft in a clockwise direction to seek the desired higher est tes settting. If a lower numbered setting of shaft I5 is to be selected, the motor will drive that shaft in a counterclockwise direction to seek this lower setting. The manually preset positions of the rings corresponding to the series of desired shaft settings, must therefore progress in the proper angular direction. Furthermore, if an attempt is made inadvertently to set one stop ring to an improper angular position with respect to the preceding stop ring, the pin and groove interlock will automatically reset the adjacent rings to maintain the proper progressive relationship.

a A typical setting of ten positions for shaft [5, expressed in angular degrees, might be as follows:

Position Position of Shaft degrees The stop rings, by means of these cooperating pins and grooves, act somewhat similar to a stack of lost-motion members, so that each ring can be manually turned during presetting, through an angle of somewhat less than 360 relative to the adjacent ring. The complete rotation of shaft i5 is limited to a single revolution, by means of the terminal stop ring M which has a lug 40 adapted to engage a fixed terminal stop 39. Consequent-. ly, noneof the stop rings can ever be manually preset to a point outside the single complete revolution of shaft (5, even though the total or cumulative adjustment of the several rings considered around the shaft 15 would be a multiple of 360. In order to preserve this necessary relationship between the various stop rings, each stop ring carries on one flat face thereof a respective pin 22A-22J, the opposite face of each ring, except ring 21A, being provided with a groove 22B-22J'. These grooves have the same radius as the radial location of the respective pins on the next adjacent disc, as shown more clearly in Figs. 5, 7, 8 and 9. As shown more clearly in the exploded view of Fig. 9, each stop ring has its groove of the same arcuate length, and thepin is located midway between the ends of the groove on each stop ring. However the angle a-be tween the interlocking pin and the stopping notch 23A on each ring, is different for successive rings. For example, considering stop ring MA as being in the #1 (or zero) position, the angle a may be whereas the angle a for the next stop ring 223 may be and so on for the remainingrings, the angle "a increasing by 25 for each ring.

In Fig. 9, the first stop ring 2 iA is in a position wherein the stopping notch 23A represents the initial or zero setting of shaft 15. The remain-. ing rings 2IB2iJ are shown in Fig. 9 in their minimum settings (that is, for a minimum incremental angle of 5 between adjacent rings), so that under this assumption the minimum setting for ring 2IJ is 45. Consequently, if the length of the grooves is 300, the maximum setting between adjacent rings is limited by the length of the groove plus 5. Thus the maximum setting for ring 2iJ will be 355. Any of the pre- Initial x Attempted Resulting Selective POSltlOD. of Shaft 15 (proper) I 1 Setting 1 Chan e Change degrees degrees degrees Note that in attempting to set position #5 to a higher value than #6, #6 willbe pushed by the pin and groove to a corresponding higher value. ,If position #5. were set still higher, #7 would also be afieotedand so on.

Mounted in spaced parallelism to shaft [5 is another shaft 2 5, which carries the selector cam drum 25 consisting of cams 25A-25J, each planarly aligned respectively with a corresponding stop ring 2|A2IJ. These cams are fixedly mounted on shaft 24 and each has an arcuately curved recess 25A'25J in its periphery, the recesses being arranged so that their centers or .low points are located on a helical path around the periphery of the cam drum. Each of; these recesses is, in accordance with one feature of the invention, in the form of a circular are which cooperates with the corresponding heel 32A--32J of the corresponding pawl ZSA-ZBJ. As a result of the helical arrangement of the recesses -25A'25J, they serve to preselect any corresponding particular one of a series of stopping .pawls Zi'iA-ZSJ. Each of thepawls is planarly aligned witha corresponding stop ring and with a corresponding cam. The pawl 26C is shown in shaft stopping position, wherein its heel 320 is riding on the low part of the'cam recess 250, thus permitting the toe 3lC to enter the slot 23cm stop ring 2IC when the ring rotates to bring slot 230 into registry with toe 3| 0. Each pawl is provided with one of a series of wire springs 28A-28J, each spring being looped around the fixed rod 29 and having its lower end (Fig. 2 in engagement with the rectangularbar 30 extending between the plates in and Il. The upper end of each spring engages the edge of the corresponding pawl, thus tending to rotate the pawl counter-clockwise as seen in Figs. 2 and 4. It will be clear from the foregoing arrangement that the toe of any pawl cannotcompletely enter a notch in the corresponding stop ring until the heel of that pawl is riding on the lower portion of the slot in the associatedcam. In other words, each cam selects or prepares its associated pawl for subsequent stopping engagement with the corresponding stop ring.

Figs. 2 and 4 show the mechanismwherein'the pawl l26C is in selected position, so that its heel 32C rests on the low portion of the slotinthe associated cam, while the toe 3 lCis in full registry with the corresponding notch 23C. In this position each remaining pawl, for example pawl 'ZGD, has its 'heel 32D resting on the non-recessed periphery of the associated can; 253, thuspre venting the toe of the pawl fromregistering with th slot n the co rf ncn j l s. stop fins .anyi. naw1; has its-toe incomplete .registry with a slot .as q r it. ii ve' ylock t e aft 15in the selected position. While the" shaft is. thu positively stopped. the drivinemotor may continue to rotate beca fse it'is coupled .to theshaftglfi-through the 'intermediar'y of a slip clutch 3,2. In order to make "sure that-the heels of .the pawls'register withthe central low part of each cam slot for each selective. setting of the: cam drum, the shaft 24 also carries, a. toothed wheel 24:; having a. series of equally-spaced notches 242); each angularly oriented varound the shaft 24-t0 GQ IGSQQnd With thecenter'of acorresponding recess 2 5A-25J. Cooperating with the whefil. Mi ls a. pawl Me which by means of sprin 2 d. en s. t en a e in any notch 24b with which it comes in registry. Thepawl 240 is h ld out of; en a ment. with the wh l 24:; y mea s f. a relay 24c, whose armature. is mechanically connected-to pawl 24c, .It. will lac-observed. that the motor shaft is coupled to shaft'214 through a slit clutch z ifto allow the motor to continue rotating until it coasts. toa. dead stop ,even'after-the shaft 2 4has been positively stopped. by pawl 240. Motor drives. agear 3.3 which in turn drives shaft-2.4 through. the. intermediary of slip" clutch- 2472A fixed terminal stop pawl 39 is mounted o as to confine. the rotation of. the corresponding terminal stop ring. 4| fastened to shaft Hiptoy-an anginlar orientationv of approximately 360; i a

' The gear, 33 also drives: the metal; ring rotor- 11. of a selectorswitch 50, of theiautoma-tic seek-- ing type. The switch 50 maybe of;- the usual. line finder type havingabrush "Ila carried by rotor 71; ThiSaS'WitChj-S provided-with a series. of fixed bank contacts equal; in number to thenumber ofcams 25 A25J. These bank; contacts; are multipled over asuitable cable to correspond-- ing fixed contactsiof; a selector switch 13; Co.- operatingwithv the fixed contacts of switch 13 are two circular rotary contactorsegments 13a, 13b, having diametrically: opposite spaced ends or gaps. 13c, 13d. The fixed or. bank. contacts: of selector switch. 13* are arranged; in equal. spaced. array around the. rotary segments, and occupy ,an-arc of somewhat. less, than 1.80. degrees. Also fixedly. mounted with respectto the rotary segments 13a, 13b,. are twobrushes'13e, 13f, which. are located diametrically opposite to each. other. The segments 13:1,.13b, can be, attached to a suitable insulatordismor drum 13g which is provided with an adjusting. handle, oryknob 13b for rotating the switch to any one of the ten sue: cessive positions. The arrangement is such that when the :gap Ii-leis inregistry with any of 1 the corresponding" fixed bank contacts of switch '13, the; brush Ha. of switch; 50 is, by theautomatic seeking action ofswitch 50, brought into registry with the corresponding fixed bank contact. of switchifl, and in this relationthe energizing circuitof relay Me is open, thus permitting pawl 240 to drop into the cooperatingnotch 24b;ands.top shaft 24, and also switchrotor 11.

In accordance with the., invention-, the. shafts 24 and 15 are; arranged to be rotated in..either a. clockwise. or counter-clockwise. direction, de-.- pending upon the-location between. a. previous setting. of the gap of switch 13, and the location of a subsequent or new setting. The sense of direction of rotation of shafts 24 and. I5 will be determined by the relation between'the fixed. brushes 13e, 13 and the orientation of the sea-- aeoaeee ments 13a, I33, with respect thereto. -Thus, in the particular setting showri'in Fig. 4, wherein the shaft I is stopped in its #3 position'by means of pawl 260, the gap 130 is injregistry with the #3 fixed'contact of switch I3,and brush 11a is in registry with #3 fixed contact of switch 50. If, for example, it is now desired to select the #2 position for shaft 24, that is where it is stopped by pawl 263, the knob [39 is merely turned from its #3 position counter-clockwise to its #2 position. In this setting the gap 130 is in registry with the #2 contact, and a circuit is traceable from the negative terminal SI of the power supply, thence via conductor 92, the energizing winding of direction control relay 93, conductor 94, brush 13f, rotary segment 13b, #3 fixedcontact, conductor 95,"#'3 fixed contact of switch 50, brush 'I'Ia, cooperating wiper brush 'I'Ib, conductor 96, winding of relay 24c, conductor 91, to the positive terminal 98 of the power supply. Relays 93' and 24e operate as a result of the closure of this circuit. Relay 93 attracts its armature 99 against the 'tensionof spring I00, and this I armature immediately latches under the latching end of armature II3I controlled by another directional .controlxrelay I02. Thus the armature 99 remains'intlatched position until relay I02'is operated. It should be observed that under the above assumed new setting of switch I3, no circuit is completed through the winding of relay I92. When. armature 99 moves to latched position, it operates the associated movable relay contacts I93, I94,into

engagement with the corresponding stationary front contacts I05, I05. At the same time, relay 24s when operated, withdraws the pawl 240 from wheel 24a, and closes the relay contacts I91, I98. As a result, a circuit is traceable from the positive terminal 98 through the field winding I09 of the motor, conductor IIB, conductor III, con.- tacts I01, I98, conductor II2, conductor 92, to the negative terminal 9I. It should be observed that the direction of current flow through the armature H3 of the motor is controlled by the contacts I03, I04, which act in the nature of areversing switch. When relay 93 is operated as above described, it closes a circuit traceable from positive terminal 98, conductor H4, contacts I93; I95, conductor H5, armature brush II6,-armature H3, armature brush III, conductor H8, conductor H9, contacts MG,- I04, conductor-I29, conductor III, contacts I01, I98, conductoriII2, conductor 92,- to the negative terminal'9 I. When the relay 93 is deenergized. however, the direction of current flowthrough the armature II3. is reversed.

From the foregoing, it will be seen that the direction of rotation'of the motor 42 and therefore of the shafts 24 and I5, is determined by the angular spacing between the previous setting of the gap 130 with respect tov any subsequent desired setting,.and as will be described hereinbelow, this direction of .mov'ementis such as to cause the shafts 24 and I5 to execute the leastamount of rotary turning to move from the previous setting to the. subsequent desired setting. However, it is important to arrange the #1 to #10 contacts ofswitch 13 in the same sequence as the correspondingsuccessive positions'to be controlled by the cams '25A-25J.

As a result of the turning of the motor in response to the new setting of. switch I3 asabove mentioned, the shaft 24 isrotated in a counterclockwise direction, as is the brush 11a of the seeking switcn50. It will be observed that one of the reasons for making the recesses 25A'-25J of rather shallow ar-cuate form, is so that the initial rotation of the shaft 24 in response to the starting of rotation of the motor 42 as above described, causes the pawl, for example pawl 26C, to be rotated clockwise, thus releasing the toe 3 IC and permittingshaft I5 to begin its counterclockwise rotation almost substantially simultaneously with the rotation of shaft 24, Each of the pawls 26A--26J has an integral arm I2 IA-I 2 IJ adapted to engage the swingable bail or bar I22. Bar I22 carries a contact member I23 which is adapted to open and close with a cooperating stationary contact I24, to provide a substitute energizing circuit for the motor which is independent of the contacts I97, I98. When all the pawls 26A-2 BJ are in unlocked position with respect to their associated stop rings, the bar I22 maintains contacts I23, I24, closed. However, as soon as any pawl, for example pawl 26B, rotates counter-clockwise (as seen in Fig. 4), with its toe (H13 in the slots 233, the arm I22 is rocked to open the contacts I23, I24.

Since, under the aboveassumption, the new setting for switch I3 is thatcorresponding to fixed contact #2, the shaft 24 and the switch rotor 11, rotate counter-clockwise until the switch brush Ila engages #2 contact. In this condition the previously described circuit for relay 93 is broken at gap I30, and relays 24c and 93 thereupon become deenergized. Consequently, the pawl 240 is retracted by its spring 24d in readiness to engage in the nearest notch 24B corresponding to the #2 position of shaft 24. However, the motor circuit is kept energized through contacts I07, I98, to insure that pawl 24c enters the said notch 24?) to positively stop further rotation of shaft 24. Consequently, only one of the series of pawls EBA-2U, namely pawl 25B, is in condition to be rotated counter-clockwise (as seen in Fig. 4) by its spring 283, since all the remaining pawls have their heels riding on the high part of their respective cams. However. shaft I5 may continue to rotate until the slot 2313 comes into registry with pawl toe 3IB, thus positively stopping shaft I5. Thereupon, the substitute motor circuit through contacts I23. I24, as above described, is broken, and the motor can coast to rest by reason of the slip clutch 32.

In the foregoing description it has been assumed that the new setting is in a counterclockwise direction from the previous setting. If the new setting had been located in a clockwise direction from the previous setting, for example if the new setting were that corresponding to position #10 of switch I3, instead of the relay 93 being operated, an energizing circuit would be closed from the negative terminal 9| through the winding of relay I92, conductor I25, brush 'I3e, segments 13a, conductor 95, #3 contact of switch 59, brush 'I'Ia, wiper 'IIb, conductor 96, relay 24c, conductor 9'! to the positive terminal 98. The energization of relay I92 operates the latch armature IGI, thus permitting armature 99 to be retracted by its spring I99, and closing a reverse circuit to the motor, causing shafts 24 and I5 to rotate in the clockwise direction. The remaining sequence of operations is then similar to that above described.

The importance of coupling the adjacent stop rings 2IA-2IJ to each other through their respective pins 22A, and grooves 22B, etc., will be clear from the foregoing. If these stop rings were entirely independently pro-adjustable around the drum [1 as in the prior Patent #2,285,414, or as disclosed "in said application Serial-No, 639,198,.there would be no assurance that the proper sequence of settings of switch I3 wouldproperly. correspond-with the sequence of settings of shaft 15. For example,-let it beassumed' that the shaft I5 is connected to the elevator controls of an aeroplane, assumingthat these controlshavebeen previously set in a #3 position as above described, and it is desired to cause the aeroplaneto descend to a lower altitude represented for exampleby position #1. With the arrangements described in the; said prior patent and application theelevators would have to return to a normal or home position, which would result in the aeroplane havingto'assume some zero or base altitude before it actually descends to position #1. Likewise, if the aeroplane were desiredto increasefits altitude to position #Tfor example, it would still be necessary for the controls to operate the aeroplane to. some base or home position before it-actually arrives at the higher altitude. In accordance with the present invention, the various positions #l to of the switch 73-are in orders of increasing spacing. In other words,- in the case of an aircraft control, they would represent different altitudes, with the lowestaltitude represented for example by position #1,- and the highest altitude represented by position #10, and with inter mediate altitudes represented by the respective intervening positions of'switchj 13. .If. the various settings of the elevator controls were equally spaced at all times, then of course the stop rings could be permanently attached toshaft. I5--with the slots 23A-.-23J located equally around. the axis ofsaid shaft. Howevenin most casesthe spacings between difierentselective settings of shaft I5 may be of unequal amounts, and yet it must be arranged .that the shaft. must always follow the same direction of rotation as the directionof rotation of switch 13. All, these conditions are met by the arrangement as above described. There is thus provided a highly accurate and flexibly adjustable automatic control arrangement for any device which is arranged to be connected to shaft l5.

It will be understood, of course, that whileparticular parts have been described herein, various changes and modifications may be made therein without departing from the spirit and scope of the invention.

, What is claimed is:

1. Apparatus of the servo type, comprising, a member manually movable to a plurality of different positions, a shaft which is to assume different rotational settings in accordance with the positions of said manually movable member, a

plurality of shaft stopping elements rotatable withsaid shaft, 21, corresponding plurality of shiftable stop'members cooperating respectively with said step elements, rotatable means for selectively setting any one of said'stop members to prepare it forstopping engagement with a corresponding stop element, a rotary switch'of the automati'ccircuit seeking type having a rotor and a plurality of bank contacts'each allotted to a corresponding one of said different positions; a motorior rotating said rotatable means and for rotating said switch rotor in unison, means responsiveto a; changed position of said manually movable member and movable as a unit therewith to cause said motor to rotate said rotatable means and said switch rotor to correspond to said changed position, the last-mentionedmeansin eluding motor control circuits completed by said manually movablemember for causingsaid I ofsaid rotary seeking switch-,said-rotor,

10 rotatable means to rotate through the shortest circular are necessary to bring it from its original setting to the setting. corresponding to said changed position, said last-mentioned means also includinga centeringwheel and cooperating latch for maintaining .saidrotatable, mea'nshin rotation until'said shaft; is accurately centered in its desired stopping position.

2. Apparatus according toclaim 1; m whichof said rotary-seeking switch. f

4. Apparatus according to claim- ,1, in which said manually movablermember is connectedfto. the rotor of a multi-contact switch,said switch having a bank of fixed contacts arranged around the rotor in less than arsemi-circular arc said. rotor also carrying a pair of substantially semi circular contact segments with diametrically-op posed gaps and a pair ofdiametrically opposite fixedbrushes to engage-said contact segmentsfor controlling the current directioninthe said motor control circuits. I 5. Apparatus according to-- claim-1, -in which said manually movable member is connected ,tothe rotor-of a multi-contacts-witchrhaving. a-bank of fixed contacts whichfiarerespectively..jelectrically connected to corresponding bankcontacts lso. carrying a pair of substantially semi-ch c liar contact segments for. engaging; the associated bank contacts, and said multi-contact switchalso having -a pair of diametrically opposite gaps and apair of diametrically opposite, brushes engaging.

said motor control circuits-includesmotor .re-

-versing switch means, a multi-contactlfswi'tchhaving a rotor connectedto -said'manually mov v able member and also having: a seriesoffixed bankcontacts electrically onnected respectively to the bank contacts of said; seekingswitch, said seeking switch having-a rotary brush for s ccessively engaging its bankcontacts, said, seeks, ing switch also having-a-common wiperconnect able to any of said bankcontacts through saidrotary brush for completing 1 acircuit to operate said motor reversing. switch.means when the angular settingof said rotary brush anaem a the manualsetting of. said manually. movable member. 1

8. Apparatus according to claim 7', in which said rotatable means is connected toa mu itoothed stopping; wheel, said; wheel having a cooperating stopping paw-1,, and; electromagnetic means for operatingsaid stoppin-g -pawhsaid electromagnetic means beingalso connectedin circuit with saidw-iper. v I

9. Servo apparatus,--cornprising, .-a manually operable "control switch having a rotor-v carrying a pair of substantiallysemi-circular contact segments" withoppositely disposed gaps abank 0f fixed-contacts arrangedaroundsaid rotor -in less than a semi-circular arc, a pair of diametrically opposite wipers for engaging said segments, a multi-point selector switch of the circuit seeking type having a rotary brush and a bank of surrounding fixed contacts, means electrically connecting the bank contacts of the control switch with the respective bank'contacts of the seeking switch, a common stationary wiper for said seeking switch and connectable with of the bank contacts of the seeking switch through the rotary brush thereof, a stop control cam drum, a stop ring drum, a plurality of stop control pawls each in cooperative alignment with a cam of said cam control and a stop ring of said stop ring drum, a single reversible motor for driving said cam drum, said stop ring drum and the rotary brush of said seeking switch, means responsive to a change in setting of said control switch to cause said motor to drive said cam drum inthe shortest circular arc to a stopping position determined by said seeking switch, a circuit for controlling the motor completed through said wiper, said circuit being opened upon the selective stopping of said cam drum,'another substitute motor circuit for maintaining the stop ring drum rotating until it is selectively stopped by a selected one of said pawls, and a common switch for said substitute motor circuit which is opened in response to the stopping engagement of the selected pawl with its corresponding stop ring.

l0. Servo apparatus according to claim 9, in which said cam drum is provided with a toothed stopping wheel, a stopping pawl for said stoppingwheel, an'electromagnet for operating said pawl in response to a change in setting of said control switch and for releasing said pawl to positively stop said cam drum when said seeking switch arrives at a position corresponding to the changed setting of said control switch, said motor being coupled to said cam drum and said stop ring drum through respective slip clutches to permit the stop ring drum to continue rotating in its selective direction even after said cam drum is stopped. Y I 7 11. 'Apparatusfor selectively positioning a rotatable shaft in any one of a series of desired stopping positions without requiring the shaft to go-first to a home position before executing its selective rotation, comprising, a plurality of shaft stop rings each having a stopping abutment and rotatable with said shaft a corresponding plurality of pivotally-mounted shaft stopping pawls, a corresponding plurality of pawl selecting cams, areversible motor for selectively setting said cams to permit only a selected one of said pawls to move into stopping position with the abutment on a corresponding stop ring, a multi-point selector switch having a plurality of settings equal in number to the numberof said shaft stopping positions, motor control circuits responsive to the movement of said switch from a previous setting to a subsequent setting to cause said shaft to rotate from its previous setting to its subsequent setting and through the shorter rotational angle,

and means tointerlock successive shaft stop rings around said shaft to maintain a progressively increasing angular orientation for each stopring with respecttothe preceding stop ring, said cams being assembled in the form of a rotatable drum, and having respective pawl receiving recesses arranged in a helical path around the drum periphery, said drum and shaft being coupled to said motor through respective slip clutches.

12. Apparatus for selectively positioning a rotatable shaft in any one of a series of desired stopping positions without requiring the shaft to go first to a home position before executing, selective rotation, comprising, a plurality of shaft stop rings each having a stopping abutment androtatable with said shaft, a corresponding plurality of pivotally-mounted shaft stopping pawls, a corresponding plurality of pawl selecting cams, a reversible motor for selectively setting said cams to permit only a selected one of said pawls to move into stopping relation with the abutment on a corresponding stop ring, a multi-point selector switch having a plurality of settings equal in number to the number of'sa'id shaft stopping positions, motor controlcircuits responsive tothe movement of said switch from aprcvious setting to a subsequent setting to cause said shaft to rotate from its previous setting to its subsequent setting and through the shorterrotati'onal angle, and means to interlock successive shaft stop rings around said shaft to maintain a progressively increasing angular orientation for each stop "ring with respect to the preceding stop ring, s'aid cams being assembled in the form of a rotatable drum, each of said cams having an arcuately-shaped pawl receiving recess with the recesses arranged in a helical path around the drum periphery, said drum and shaft being coupled to said motor through respective slip clutches, a toothed wheel rotatable as a unit with the .drum and having a series of notches each correlated with the center of a corresponding cam recess, and an electromagnetically-controlled pawl for shiftably en gaging with said wheel forthe urposedescribed.

13. Apparatus for selectively positioning a rotatable shaft in any one of a series of desired stopp ng positions, comprising, a plurality of shaft stop elements movable as a unit with said shaft but each individually and presettably locked at different angular orientations withrespect to the shaft axis, means for interlocking successive stop elements to limitthe relative angular presettability of each stop element with respect to the remaining stop elements while maintaining each stop element oriented to a greater angular extent around said'shaft with relation to the orientation of the next preceding stopelement, a corresponding plurality of shiftable stop members one for each of said stop elements, means to selectively set any desired one of said stop members to prepare it for stopping engagement with the corresponding stop element to stopsaid shaft, and means to cause-said shaft to rotate ineither direction as determined by the shortest rotational angle between a previous selective position of the shaft and a desired subsequent selected position thereof, said stop elements being in the form of rings each having a stopping abutment for cooperation respectively with a corresponding stop member, said rings being provided on their adjacent faces with cooperating pins and grooves to limit said angular presettability.

14. Apparatus for selectively positioning a rotatable shaft in any one of a series of desired stopping positions, comprising, a plurality of shaft stop elements movable as a unit with said shaft but each individually and presettably locked at different angular orientations with respect to the shaft axis, means for interlocking successive stop elements to limit the relative angular presettability of each stop element with respect to the remaining stop elements while maintaining each stop element oriented to a greater angular extent around said shaft with relation to the orientation of the next preceding stop element, a corresponding plurality of shiftable stop members one for each of said sto elements, means to selectively set any desired one of said stop members to prepare it for stopping engagement with the corresponding stop element to stop said shaft, and means to cause said shaft to rotate in either direction as determined by the shortest rotational angle between a previous selective position of the shaft and a desired subsequent selected position thereof, and said limiting means limits the presettability of each stop ring through a maximum angle of somewhat less than 360.

HORST M. SCHVVEIGI-IOFER. ROSS S. PYLE.

REFERENCES CITED The following references are of record in the file of this patent:

Number Number France May 16, 1951 

